1. Field of Invention
The invention relates to a DC brushless voice-coil vibration motor. By changing the designs of the stator and rotor in a motor, a miniaturized DC brushless voice-coil vibration motor can gain vibrational energy by having the rotor installed off the motor center.
2. Related Art
The mobile phone can provide on-to-one distant communication. Due to its small volume and light weight, it has become one of the most popular high-tech electronics of the century.
Usually, notifying the user incoming messages can be achieved by two methods: the ring-on mode and the vibration mode. In the ring-on mode, the mobile phone turns on ring or music when there is an incoming message. In the vibration mode, a vibration motor installed in the mobile phone starts to vibrate when an incoming message is received so that the user can feel the vibration of the mobile and answer the phone call.
The currently available vibration motor is shown in, for example, FIG. 1. The vibration motor has a cylindrical shape with a weight attached to the motor axis. When the motor rotates, the weight also rotates to generate vibrational energy. However, as the electronics such as notebook computers, PDA""s (Personal Digital Assistant), mobile phones become lighter, thinner, shorter and smaller, the volume occupied by the conventional vibration motor greatly limits the designs of these high-tech electronics.
To minimize all electronic components in the vibration motor will be ideally an attempt to decrease its volume. Nevertheless, such an idea is not feasible because there might be difficulty in assembly after the miniaturization. Such limitations render the problems that are bound to be encountered after the miniaturization of the motor. Even if the assembly is possible, the difficulty in assembly may increase the cost.
Furthermore, the vibration is generated by attaching a weight to one end of the motor axis. Therefore, the dimensions of the weight object define the size of motor. As shown in FIG. 1, the weight is situated on one side of the motor, the part that generates vibrational energy is just xc2xcof the whole motor. The vibration is thus local but not global. The motor has to output a larger power so as to rotate the weight and thereby increasing unnecessary power consumption. Since the weight object is fixed on the motor axis, the output vibration efficiency is also fixed. So one has to use different motors on different models of electronics in order to generate desired vibration.
In view of the foregoing, the invention provides a miniaturized DC brushless voice-coil vibration motor. It mainly consists of a circuit board, at least two inductance coils, a weight object, a controller and at least two magnetic bolts. The inductance coils are installed on the circuit board by winding around in the radial direction and is electrically connected to the power input port on the circuit board. The magnetic bolts are situated between the two inductance coils. The weight object is installed on the inductance coils, slightly off the motor center. It is a permanent magnet with a plurality of coplanar magnetic poles. The controller installed on the circuit board between the two inductance coils functions to change the magnetic properties of the inductance coils, determining whether the motor is on or off. When current pass through the inductance coils and generates a magnetic field, the magnetic bolts disturb the static balance of the magnetic field inside the motor. Under the electromagnetic interactions between the inductance coils and the weight object, the weight object rotates and gains rotational energy. Since the weight object is displaced off the motor center, the rotational energy of the weight object turns into vibrational energy of the motor.
The weight object functions as the rotor inside the motor and generates vibrational energy so that the motor can generate vibrational energy in all directions. It lowers the power consumption when starting the motor and increases the operational efficiency of the vibrational motor.
The weight object in the invention can have different displacements from the motor center to generate different vibration levels for different models of electronics.